This section provides background information related to the present disclosure which is not necessarily prior art.
FIG. 1 shows an exemplary embodiment of the semiconductor light emitting device disclosed in U.S. Pat. No. 7,262,436, in which the semiconductor light emitting device includes a substrate 100, an n-type semiconductor layer 300 grown on the substrate 100, an active layer 400 grown on the n-type semiconductor layer 300, a p-type semiconductor layer 500 grown on the active layer 400, electrodes 901, 902 and 903 formed on the p-type semiconductor layer 500, with the electrodes serving as reflective films, and an n-side bonding pad 800 formed on the n-type semiconductor layer 300 which had been etched and exposed.
A chip having the above structure, i.e. a chip where all of the electrodes 901, 902 and 903, and the electrode 800 are formed on one side of the substrate 100, with the electrodes 901, 902 and 903 serving as reflective films, is called a flip chip. The electrodes 901, 902 and 903 are made up of an electrode 901 (e.g., Ag) having a high reflectance, an electrode 903 (e.g., Au) for bonding, and an electrode 902 (e.g., Ni) for preventing diffusion between materials of the electrode 901 and materials of the electrode 903. While this metal reflective film structure has a high reflectance and is advantageous for current spreading, it has the drawback that the metal absorbs light. In addition, even if the metal reflective film could serve as an electrode and heat-emission passage at the same time, it is not easy for the metal reflective film to serve as an electrode and have an excellent heat-emission structure at the same time.
FIG. 2 shows an exemplary embodiment of the semiconductor light emitting device disclosed in JP Laid-Open Pub. No. 2006-20913, in which the semiconductor light emitting device includes a substrate 100, a buffer layer grown on the substrate 100, an n-type semiconductor layer 300 grown on the buffer layer 200, an active layer 400 grown on the n-type semiconductor layer 300, a p-type semiconductor layer 500 grown on the active layer 400, a light transmitting conductive film 600 with a current spreading function, which is formed on the p-type semiconductor layer 500, p-side bonding pad 700 formed on the light transmitting conductive film 600, and an n-side bonding pad 800 formed on the n-type semiconductor layer 300 which had been etched and exposed. Further, a DBR (Distributed Bragg Reflector) 900 and a metal reflective film 904 are provided on the light transmitting conductive film 600. While this structure shows reduced light absorption by the metal reflective film 904, it has the drawback that current spreading is not facilitated, as compared with the structure using the electrodes 901, 902 and 903.